Alcohol is one of the most addicting substances on Earth. Alcoholism is so prevalent and can be so disruptive to society that the United States once succeeded in banning it. Remnants of the Prohibition and America's puritanical founding can still be seen in the "blue laws" of many areas. It is often an underlying factor in traffic accidents and violent crime. But if alcohol can cause such egregious behavior and cause debilitating health problems, why do alcoholics keep drinking? A new study from the University of California, San Francisco has scientifically uncovered the truth behind alcohol addiction. The answer lies in endorphins, naturally produced chemicals in the brain that create opiate-like effects.

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The study marks the first time that endorphin release has been directly observed in two sections of the brain: the nucleus accumbens and orbitofrontal cortex. The exact locations of endorphin production may be instrumental in targeting the development of more effective drugs to combat alcohol addiction, according to senior author, Howard L. Fields, M.D., Ph.D.

The researchers used a group of 13 heavy drinkers and a control group of 12 non-heavy drinkers. Using PET imaging (positron emission tomography), they observed the alcohol's effects on the brain.

For all subjects, the alcohol led to a flood of endorphins. When the endorphins were released in the nucleus accumbens, the subjects expressed greater feelings of pleasure.

When more endorphins were released in the orbitofrontal cortex, the heavy drinkers felt more intoxicated, while the non-heavy drinkers did not.

"This indicates that the brains of heavy or problem drinkers are changed in a way that makes them more likely to find alcohol pleasant, and may be a clue to how problem drinking develops in the first place," said lead author, Jennifer Mitchell. "That greater feeling of reward might cause them to drink too much."

The researchers linked the endorphin release to certain opioid receptor sites in the brain, which they mapped out using a radioactive chemical called carfentanil. When the carfentanil encountered the endorphins at the receptor sites, it lights up on the PET image.

This finding will greatly aid in developing a medical treatment for alcohol abuse by directly targeting the specific opioid receptors.

The study has been published in the journal, Science Translation Medicine.